Heretofore there have been many approaches to the control of the stroke of the piston in air driven power cylinders and many of these prior constructions have involved various types of air cushioning action obtained inside the cylinder as it approaches the end of a power stroke. Some efforts have been made to provide internal controls for adjusting the length of stroke of a piston in a power cylinder and some prior apparatus is shown in U.S. Pat. Nos. 2,614,536 and 2,922,397 on auxiliary piston means inside the cylinder unit to control the length of stroke of the piston. However, these prior constructions are relatively complex and expensive and do not have maximum life and freedom from maintenance requirements.
One particular use of an adjustable stroke air cylinder is in the packaging of articles, particularly the packing of a plurality or group of bottles in a case-filling machine wherein the bottles are arranged in a group for case-filling action such as by the mechanism shown in U.S. Pat. No. 3,052,071, after which grouping of the articles, they are dropped down through a grid in the apparatus to be received into an empty container or case positioned below the case-filling area of the machine. Usually an empty case is fed to a case-lifter mechanism that receives the case, lifts it up to a position adjacent to the case-filling grid that drops articles down into the case, and then the case-lifter drops the filled case down for other processing. In an apparatus of this type, the case-lifting means have been of various types, including the construction shown in reissue U.S. Pat. No. 26,906. While these case-lifter means have been operative and give good service for some time, it obviously is desirable to have an improved, easily adjustable case-lifter device available. An adjustable length stroke cylinder for controlled power lift drive actions can find a number of different uses in the marketplace, including those in case-filling actions.